gdford:
To change an Object to a Lamp: open the library part via File > Libraries and Objects > Open Object..., then in the Main Library Part window click on the Select Subtype... button and change the subtype to Model Element > Electrical > Light. This will add the Light parameters to the part, but not the necessary code to the 3D Script (
Light command) to be a light source. If you are comfortable with writing GDL, you can add the necessary code. If you are not conversant with GDL, then it will be simpler to keep the part as an Object for the model, and use one of the generic Lamp parts (in the General Light Sources folder) as a light source for the renderings.
You should add a Signature to your Profile (click the Profile button near the top of this page) with your ArchiCAD version and operating system (see mine for an example) for more accurate help in this forum.
David